Conventionally, a microcapsule type adhesive for adhering a threaded member such as screw, bolt, nut and machine screw is widely known. For example, the microcapsule type adhesive includes a microcapsule type adhesive for locking comprising (A) a microcapsule comprising epoxy resin as a core material and aldehyde-based resin or urea-based resin as a wall material, (B) a binder comprising water-soluble polyacetal resin and (C) a nonvolatile and water-soluble or water-dispersable amine-based curing agent (Patent Document 1); a microcapsule type adhesive composition comprising (A) a microcapsule comprising epoxy resin as a core material and aldehyde-based resin or urea resin as a wall material, (B) an emulsion with a pH of 6 to 13 comprising binder resin with emulsifying ability, (C) a water-soluble or water-dispersable amine-based curing agent, and (D) a hydrolytic neutralized product of a copolymer obtained from alkyl vinyl ether and maleic anhydride, or a hydrolytic neutralized product of crosslinked alkylidene of the copolymer obtained from alkyl vinyl ether and maleic anhydride (Patent Document 2); a locking agent composition in a form of an aqueous dispersion including a microcapsule type adhesive for applying to a screw-type fastening fixture containing a microcapsule with a wall material including urea-based resin, melamine-based resin, urethane-based resin, polyurea-based resin, polyamide-based resin, epoxy-based resin, or copolymer resin obtained from the two or more resins into which epoxy resin as a reactive adhesive or a mixture of epoxy resin and a reactive diluent is enclosed, and an emulsion or a dispersion in which liquid or semi-solid polyamide with a free amino group acting as a curing agent for the epoxy resin (reactive adhesive) and as a binder (binding agent) for the microcapsule is emulsified or dispersed in water or in a mixture of water and lower alkanol as an aqueous dispersion medium containing a dissolved emulsifier or dispersing agent, wherein the microcapsule is dispersed in the emulsion or the dispersion (Patent Document 3); and the like. In all these adhesives, adhesive resin such as epoxy resin is enclosed into a microcapsule to interrupt contact with a curing agent, for acquiring high preservation stability. Although this causes to some extent high preservation stability and fixing force, the preservation stability and fixing force are still not enough, so there is room for improvement.
A liquid composition for applying a thread groove is known, the composition comprising a consistent viscous liquid composition formed by uniformly dispersing a microcapsule encapsulating a lubricant in a liquid or semi-solid state at room temperature and a microcapsule encapsulating an epoxy resin-based adhesive in a liquid or semi-solid state at room temperature, in a liquid phase which is a viscous solution obtained by dissolving an elastomeric substance as a main component of a pressure sensitive adhesive and a curing agent for the epoxy resin-based adhesive into an organic solvent or a mixed solvent of a water-miscible organic solvent and water with or without addition of a tackifier, or in a liquid phase which is a viscous aqueous emulsion or a viscous aqueous dispersion obtained by dispersing the elastomeric substance and the curing agent in water or an aqueous medium with or without addition of the tackifier (Patent Document 4). In Patent Document 4, it is described that polyamide and polythiol can be used as the curing agent for the epoxy resin-based adhesive. Furthermore, in the liquid composition for applying a thread groove described in Patent Document 4, the curing agent is required to have consistency as well as action for curing by reaction with the epoxy resin. Due to the consistency, the liquid composition will achieve various effects by adhering the microcapsule encapsulating the lubricant and the microcapsule encapsulating the epoxy resin-based adhesive to an adherend well without being dried out and generating a solid powder chip after applying and drying the liquid composition for applying a thread groove to a screw. Therefore, the curing agent must exhibit the consistency between the above microcapsules and the adherend, so the liquid composition for applying a thread groove cannot achieve the above effects by encapsulating the curing agent into the microcapsule. For this reason, in Patent Document 4, there is not a technical idea of encapsulating the curing agent into the microcapsule. Furthermore, in Patent Document 4, it is not described that the curing agent can be encapsulated into the microcapsule.
A microcapsule type curing agent essentially comprising (A) a curing agent for thermosetting resin and (B) thermoplastic resin which is heat dissoluble into the thermosetting resin, wherein the component (A) is a particle coated with a layer containing the component (B) as a main component and an average particle diameter thereof is 0.1 to 20 μm, is disclosed (Patent Document 5). The thermosetting resin includes epoxy resin, cyanate ester resin, maleimide resin, and resin obtained by preliminary reaction of cyanate ester resin and maleimide resin, and the curing agent for the thermosetting resin includes aliphatic amine, alicyclic amine, aromatic amine, polyamide, an urea compound, an imidazole compound, a guanidine compound, a hydrazide compound, an acid anhydride, a Lewis acid complex, a phenolic compound and a mercaptan compound. The invention provides a thermosetting resin composition which can exhibit good preservation stability at room temperature and excellent heat resistance of a cured article, and a microcapsule type curing agent for providing a prepreg. In Patent Document 5, although the mercaptan compound is included in a great number of the substances listed as the curing agent, there is not an example in which a microcapsule type curing agent containing the mercaptan compound is used.
A photosensitive microcapsule is known, the microcapsule comprising a wall forming substance which encapsulates an internal phase including a photosensitive composition, the photosensitive composition being able to be cured by free-radical initiated addition polymerization or crosslinking, and the photosensitive microcapsule encapsulating polythiol (Patent Document 6). The photosensitive microcapsule contains the photosensitive composition and polythiol in a capsule. In Tables A to E shown as examples, polythiol, namely trimethylol propane tris (β-mercapto propionate) (TMPTMP) and pentaerythritol tetrakis (β-mercapto propionate) (PTEMP), is encapsulated into the capsule in addition to trimethylol propane triacrylate (TMPTA), a diallyl o-phthalate prepolymer (DAPP) and bisphenol A epoxy resin (DER662). For example, in C-3 of Table C, trimethylol propane triacrylate and bisphenol A epoxy resin are encapsulated into the microcapsule with polythiol, namely trimethylol propane tris (β-mercapto propionate). Thereby, action effect as the photosensitive composition, for example film velocity, is improved.